1. Field of the Invention
The present invention generally relates to information delivery systems, and particularly relates to an information delivery system which delivers information from an information center to respective terminals.
2. Description of the Related Art
Conventional satellite communication systems are used for transmitting broadcasting signals towards a large number of anonymous users as used in a broadcasting satellite system, and every receiver (user) receives the same information, which is in turn displayed on a screen.
Another usage of satellite communication systems is to transfer a large amount of data to a specified base center.
In such conventional satellite communication systems, information is either transmitted to a large number of anonymous receivers or transferred to a specified base. Such usage of the conventional satellite communication systems covers a weak point of ground networks such as Internet and Intranet. When a large amount of data is attempted to be downloaded through a network such as Internet or Intranet, such an attempt will turn out to be impractical because of a prohibitingly lengthy time required for the downloading, and will create a large amount of traffic, which may seriously affect main business communications with regard to accounting, sales, telephoning, etc. In consideration of this, integration of a satellite communication system with a ground network system should prove to be beneficial.
FIG. 1 is an illustrative drawing showing an information delivery system which integrates a satellite communication system with the Internet and a public telephone network.
The information delivery system of FIG. 1 includes a terminal 101, a public telephone network 102, a user center 103, Internet 104, a terminal 105, a satellite-data-communication ground base 106, and a communication satellite 107.
An example to be described here is a case in which the same information needs to be delivered from the terminal 105 to a plurality of terminals inclusive of the terminal 101 which are scattered around in a large area. In a case of a business corporation, the plurality of terminals including the terminal 101 may be computers installed in its branches and local offices, and a corporate information center updates data of databases all at once with respect to these branches and local offices. Such a case is hereinafter referred to as a push-type service.
In the case of the push-type service, the terminal 105 requests broadcasting from the satellite-data-communication ground base 106 by transmitting a destination file and a real file to the satellite-data-communication ground base 106 via Internet 104 and the user center 103. The real file includes the contents of information which is to be delivered to the terminal 101, and the destination file indicates a destination to which the real file is to be delivered.
The satellite-data-communication ground base 106 delivers the real file to the indicated terminal 101 via the communication satellite 107 in accordance with conditions set forth in the destination file. When errors are found in the received data, the terminal 101 issues a request for a repeat of data transmission to the satellite-data-communication ground base 106 via the public telephone network 102. Upon receiving the request, the satellite-data-communication ground base 106 sends the same data again to the terminal 101 via the communication satellite 107. After data transfer is repeated a predetermined number of times, the satellite-data-communication ground base 106 notifies the terminal 105 of results of data transfer since the terminal 105 initially requested broadcasting.
FIG. 2 is an illustrative drawing showing another type of service using an information delivery system which integrates a satellite communication system with a public telephone network.
The information delivery system of FIG. 2 is basically the same as that of FIG. 1, and the same elements as those of FIG. 1 are referred to by the same numerals. FIG. 2 is used for explaining a case in which the terminal 101 issues a request to receive data via the communication satellite 107 when the terminal 101 needs to download a large amount of data. Such a case is hereinafter referred to as a pull-type service.
In the case of the pull-type service, the terminal 101 sends a request for data transmission to the satellite-data-communication ground base 106 via the public telephone network 102. The satellite-data-communication ground base 106 obtains an IP (internet protocol) address of the terminal 101 and an IP address to which a connection needs to be established, and establishes a connection to the user center 103 which has the above IP address. The user center 103 transfers a real file to the satellite-data-communication ground base 106 as this real file is requested.
The satellite-data-communication ground base 106 obtains a satellite-network address of the terminal 101 based on the IP address of the terminal 101, and delivers the real file to the terminal 101 via the communication satellite 107. When errors are found in the received data, the terminal 101 issues a request for a repeat of data transmission to the satellite-data-communication ground base 106 via the public telephone network 102. Upon receiving the request, the satellite-data-communication ground base 106 sends the same data again to the terminal 101 via the communication satellite 107.
The push-type service of FIG. 1 has drawbacks in terms of security, reliability, and costs because a request for a repeat of data transmission is made via a public telephone network. Even when the number of receiver terminals in need of another data transfer is small and only a small amount of data transfer is needed, data transfer will be repeated by using the communication satellite 107, which incurs a large cost as fees from use of the satellite. When a satellite network is congested, further, another data transfer may need to wait at the end of a queue. Further, results of data transmission are not notified unless all the data delivery including a repeat of data transfer is completed, so that an intermediate report cannot be obtained.
The pull-type service of FIG. 2 also has drawbacks in terms of security, reliability, and costs because a request for data transmission and a request for a repeat of data transmission are made via a public telephone network. Further, the communication satellite 107 is always used for data transmission, thereby resulting in an accumulated large fee for use of the satellite.
Accordingly, there is a need for an information delivery system which delivers information to terminals via a communication satellite at a low cost while maintaining security.
Accordingly, it is a general object of the present invention to provide an information delivery system which can satisfy the need described above.
It is another and more specific object of the present invention to provide an information delivery system which delivers information to terminals via a communication satellite at a low cost while maintaining security.
In order to achieve the above objects according to the present invention, an information delivery system includes terminals receiving data via a satellite-communication system, and a user center having a destination-conversion table which lists a satellite-system receiver ID with respect to each ground-network address of the terminals, and, upon receiving a request for data delivery via an intra-network, obtaining satellite-system receiver IDs from ground-network addresses indicated as destinations of the data delivery by referring to the destination-conversion table so as to deliver requested data and a reception-control program to the destinations via the satellite-communication system. The terminals use the reception-control program to check the data-reception conditions when receiving the requested data and the reception-control program, and send a request for a repeat of the data delivery to the user center via the intra-network if the data-reception conditions are not satisfactory.
In the information delivery system described above, a public telephone network is not used, so that tight security can be maintained. Further, an intra-network which is already in place can be used in place of the public telephone network, thereby eliminating costs charged for use of the public telephone network.
According to one aspect of the present invention, an information delivery system includes a user center having a destination-conversion table which lists a satellite-system receiver ID with respect to each ground-network address of terminals and an information-definition table which specifies data to be delivered via a satellite-communication system, and, upon receiving a request for data delivery via an intra-network, obtaining one or more satellite-system receiver IDs from one or more ground-network addresses indicated as one or more destinations of the data delivery by referring to the destination-conversion table, so as to deliver requested data to the one or more destinations via the satellite-communication system only if the requested data is specified in the information-definition table.
In the information delivery system described in the above, if the requested data is not specified in the information-definition table, the requested data can be delivered via the intra-network. Since data delivery is made by using an appropriate route after selecting one of the satellite-communication system and the intra-network, costs for use of the satellite-communication system can be reduced.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.